1. Field of the Invention
The present invention generally relates to the production of fuels from biomass, and more particularly to methods and systems for measuring materials to control the production of fuels.
2. Discussion of the Background
The use of solid fuels is the world's largest energy market. In the United States, solid fuels are used primarily for generating electric power and in metallurgic and cement manufacturing processes. This market is dominated by non-renewable resources, principally coal, and to a lesser extent petroleum coke. Biomass sources, which are generally considered to be renewable, form less than 5% of the U.S. Market.
There is an urgency to switch to energy sources that will have less of an environmental impact, especially with regards to the emission of greenhouse gases. Biomass sources are an attractive alternative to conventional solid fuels, but high transportation costs and low energy density of the biomass materials have hindered their widespread use.
Methods to improve the fuel value and physical properties of biomass range include drying the biomass to remove moisture without chemically altering the biomass, and producing charcoal from the biomass, where the biomass is chemically altered into fixed carbon. Drying is accomplished at temperatures below 120° C., while charcoal production requires temperatures above 500° C. Both drying and producing charcoal are incomplete solutions, and do not enable the access to remote biomass resources.
Drying the biomass combined with grinding and pelletizing the resultant fuel produces a fuel with energy density of between 7,000 Btu per pound (16,000 kJ/kg) and 8,000 Btu per pound (19,000 kJ/kg), and a density of 0.6 g/cm3 (600 kg/m3) and 1 g/cm3 (1,000 kg/m3), and is something of an improvement. However the pellets are intolerant to water, are capable of spontaneous combustion, and are thus difficult to store.
Producing charcoal is inefficient, with only 20% to 30% of the energy in the original biomass preserved in the charcoal. So much energy is lost that producing charcoal for fuel is discouraged except for use in metallurgical processes, where it is mandatory and thus unavoidable. In addition, densifying charcoal requires a binder, a severe limitation when operating remotely. In either case, the resultant fuel is unsatisfactory for widespread application to industrial combustion processes.
One approach to facilitate the use of biomass as solid fuel is to utilize a process to convert biomass to biofuel. In a process to convert biomass to biofuel, the quantity and properties of the output biofuel and intermediate products will depend on the properties of the input biomass and the applied process parameters. Since input biomass can be variable and not well-characterized with respect to properties such as plant species, moisture content and particle size, among others, there is a significant risk that important properties of the produced biofuel, such as energy density, will be poorly controlled, variable and uncharacterized. This is undesirable and will yield low quality fuel.
Thus there is a need in the art for a method and apparatus to monitor processed material properties at one or more locations in the conversion process and to utilize those measurements to control process parameters, to produce output product with desired properties and/or to quantify important biofuel properties.